BB's work fine as a regular phone using a prepaid SIM, trying to get the data aspect to work was a pain in the bum, I might've had APN issues though. They most definitely work as plain old prepaid phones though.

If they've been activated on a BES, you'll may need to do a full device-wipe before you can put a non-BES email account on, it's possible the option to do so was removed by the admin.